Life's Irreducible Structure Author(s): Michael Polanyi Source: Science, New Series, Vol. 160, No. 3834 (Jun. 21, 1968), pp. 1308-1312 Published by: American Association for the Advancement of Science Stable URL: http://www.jstor.org/stable/1724152 Accessed: 15-07-2015 16:00 UTC

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This content downloaded from 128.103.149.52 on Wed, 15 Jul 2015 16:00:49 UTC All use subject to JSTOR Terms and Conditions whereas the second is of the machino type. By shifting our attention, we may sometimes change a boundaryfrom one type to another. Life's IrreducibleStructure All communicationsform a machine type of boundary, and these boundaries form a whole hierarchy of consecutive Live mechanismsand informationin DNA are boundarzr levels of action. A vocabulary sets boundary conditions on the utterance conditionswith a sequenceof boundariesabove them. of the spoken voice; a grammar har- nesses words to form sentences, and the sentences are shaped into a text which Michael Polanyi conveys a communication. At all these stages we are interested in the bounda- ries imposed by a comprehensiverestric- tive power, rather than in the principles If all men were exterminated, this So the machine as a whole works harnessed by them. would not aSect the laws of inanimate under the control of two distinct prin- nature. But the production of machines ciples. The higher one is the l?rinciple would stopS and not until men arose of the machine's design, and this haru L;ving Mechanisms Are Classed again could machines be formed once nesses the lower one, which consists in with Machines rnore.Some animals can produce tools, the physical-chemical processes orl lbut only men can construct machines; which the machine relies. We com- From machines we pass to living machines are human artifacts, made of monly form such a two-leveled struc- beings, by remembering that animals inanimate material. ture in conducting an experiment; but move about mechanically and that they The Oxford Dictionary describes a there is a difference between construct- have internal organs which perform tnachine as 6'an apparatus for applying mg* a macnlne. * ancl. rlgglng* . up an ex- functions as parts of a machine do tnechanicalpower, corlsistingof a num periment. The experimenter imposes functions which sustain the life of the lber of interrelated pa.rts, each having restrictions on nature in order to organism,much as the proper function- a definite function." It might be, for obsenre its behavior under these restric- ing of parts of a machine keeps the e;ample, a machine for sewing or printS tions, while the constructor of a ma- machine going. For centuries past, the ing. Let us assume that the power driv- chine restrictsnature in order to harnes workings of life have been likened to ing the machine is built in, and its workings.- But we may borrow a the working of machines and physiology lisregard the fact that it has to be re- tetm from physics and describe both has been seeking to interpret the orga- newed from time to time. We can say, these useful restrictions of llature as nism as a complex network of mecha- then, that the manufacture of a ma- the imposing of boundaryconditions on nisms. Organs are, accordingly, defined chine consists in cutting suitably shaped the laws of physics and chemistrye by their life-preservingfunctions. parts and fitting them together so that Let me enlarge on this. I have ex- Any coherent part of the organism their joint mechanical action should emplified two types of boundaries. In is indeed puzzling to physiology and serve a possible human purpose. the machine our principal interest lay also meaningless to pathology-until The structure of machines and the in the eSects of the boundary condi the way it benefits the organism is dis- working of their structure are thus tions, while in an experimental setting covered. And I may add that any de- shaped by man, even while their ma- we are interested in the natural l?roc scription of such a system in terms of terial and the forces that operate them esses controlled by the boundaries. its physical-chemical topography is obey the laws of inanimate nature. In There are many common examples of meaningless,except for the fact that the constructing a machine and supplying both types of boundaries. When a description covertly may recall the it with I?ower,we harness the laws of saucepan bounds a soup that we are system's physiological interpretation- nature at work in its material and in its cooking, we are interested in the soup; much as the topography of a machine driving force and make them serve our and, likewise, when we observe a re- is meaningless until we guess how the purpose. action in a test tube, we are studying device works, and for what purpose. This harness is not unbreakable;the the reaction, not the test tute. The In this light the organism is shown strtlcture of the machine, and thus its reverse is true for a game of chess. The to be, like a machine, a system which working, can break down. But this will strategy of the player imposes bound works according to two different prin- not affect the forces of inanimate aries on the several moves, which folZ ciples: its structureserves as a boundary nature on which the operation of the low the laws of chess, but our interest condition harnessingthe physical-chemi- machine relied; it merely releases them lies in the boundaries-that is, in the cal processes by which its organs per- from the restriction the machine im- strategy, not in the several moves as form their functions. Thus, this system posed on them beforc it broke down. exemplificationsof the laws. And simi- may be called a system under dual larly, when a sculptor shapes a stone control. Morphogenesis,the process by The author is a former Fellow of Merton Col- lege, Oxford, and Emeritus Professor of social or a painter composes a painting, our which the structureof living beings de- studies at the University of Manchester, where interest lies in the boundaries imposed velops, can then be likened to the he had previously held the Chair of Physical Chemistry. His present address is 22 Upland on a material, and not in the material shaping of a machine which will act Park Road, OxfordSEngland. This article is an itself. as a boundaryfor the expandedversion of a paper presented20 Decem- laws of inanimate ber 1967 at the New York meeting of the AAAS. We can distinguish these two types nature. For just as these laws serve the The-Xrst half of the article was anticipatedin a paper published in the August 1967 issue of of boundaries by saying that the Erst machine, so they serve also the devel- Chemical and Engineering lVelvs. represents a test-tube type of boundary oped organism.

1308 SCIENCE, VOL. 160

This content downloaded from 128.103.149.52 on Wed, 15 Jul 2015 16:00:49 UTC All use subject to JSTOR Terms and Conditions A boundary condition is always ex- tive basic bindings having the same DNA Acts as a Bluepnnt traneousto the process which it delimits. probability of occurrence. In Galileo's experimentson balls rolling Let us be clear what would happen But there remains a fundamental down a slope, the angle of the slope in the opposite case. Suppose that the point to be considered. A printed page was not derived from the laws of me- actual structure of a DNA molecule may be a mere jumlbleof words, and chanics, but was chosen by Galileo. were due to the fact that the bindings it has then no information content. So And as this choice of slopes was ex- of its bases were much stronger than the improbability count gIves the pos- traneous to the laws of mechanics, so the bindings would be for any other sible, rather than the actual, informa- is the shape and manufacture of test distributionof bases, then such a DNA tion content of a page. And this applies tubes extraneous to the laws of chem- molecule would have no information also to the information content attrib- istry. content. Its codelike character would uted to a DNA molecule; the sequence The same thing holds for machine- be effaced by an overwhelming redun- of the bases is deemed meaningful only like boundaries; their structure cannot dancy. because we assume with Watson and be defined-in terms of the laws which We may note that such is actually the Crick that this arrangement generates they harness. Nor can a vocabulary case for an ordinarychemical molecule. the structure of the oSspring by en- determine the content of a text, and Since its orderly structure is due to a dowing it with its own information so on. Therefore, if the structure of maximum of stability, correspondingto content. living things is a set of boundary con- a minimum of potential energy, its This brings us at last to the point that ditions, this structure is extraneous to orderlinesslacks the capacity to function I aimed at when I undertook to analyze the laws of physics and chemistry as a code. The patternof atoms forming the information content of DNA: Can which the organism is harnessing.Thus a crystal is another instance of complex the control of morphogenesis by DNA the morphology of living things tran- order without appreciable information be likened to the designing and shaping scends the laws of physics and chem- content. of a machine by the engineer?We have istry. There is a kind of stability whicb seen that physiology interprets the or- often opposes the stabilizingforce of a ganism as a complex network of mech potential energy. When a liquid evapow anisms, and that an organism is like DNA Information Generates rates, this can be understood as the in- a machine a system under dual con- Mechanisms crease of entropy accompanying the trol. Its structure is that of a bound- dispersion of its particles. One takes ary condition harnessing the physical- But the analogr between machine this dispersive tendency into account chemical substanceswithin the organism components and live functioning organs by adding its powers to those of poten- in the service of physiological functions. is weakened by the fact that the organs tial energy, but the correction is neg- Thus, in generating an organism, DNS are not shaped artificially as the parts ligible for cases of deep drops in initiates and controls the growth of a of a machine are. It is an advantage, potential energy or for low tempera- mechanismthat will work as a boundary therefore, to find that the morphogenetic turesS or for both. We can disregard condition within a system under dual process is explained in principle by the itS to simplify matters, and say that control. transmission of information stored in chemical structures established by the And I may add that DNA itself DNA, interpretedin this sense by Wat- stabilizing powers of chemical bonding is such a system, since every system son and Crick. have no appreciable information con- conveying information is under dual A DNA molecule is said to represent tent. control, for every such system restricts a code that is, a linear sequence of In the light of the current theory of and orders, in the service of convey- items, the arrangementof which is the evolution, the codelike structure of ing its information, extensive resources information conveyed by the code. In DNA must be assumed to have come of particulars that would otherwise the casevof DNA, each item of the about by a sequence of chance varia- be left at random, and thereby acts series consists of one out of four al- tit ns established by natural selection. as a boundary condition. In the case ternative organic bases (1). Such a code But this evolutionary aspect is irrele- of DNA this boundary condition is a will convey the maximum amount of vant here; whatever may be the origin blueprint of the growing organism information if the four organic bases of a DNA configuration,it can function (2) have equal probability of forming any as a code only if its order is not due We can conclude that in each em- particularitem of the series. Any differfi to the forces of potential energy. It bryonic cell there is present the dupli- ence in the binding of the four alter- must be as physically indeterminate as cate of a DNA molecule having a linear native bases, whether at the same point the sequence of words is on a printed arrangement of its bases an arrange- of the series or between two points of page. As the arrangementof a printed ment which, being independent of tha the series, will cause the information page is extraneous to the chemistry of chemical forces within the DNA mole conveyed by the series to fall below the printed page, so is the base se- cules, conveys a rich amount of mean- the ideal maximum. The information quence in a DNA molecule extraneous- ingful information. And we see that content of DNA is in fact known to to the chemical forces at work in the when this information is shaping the be reduced to some extent by redun- DNA molecule. It is this physical in growing embryo, it produces in it dancy, but I accept here the assumption determinacy of the sequence that pro- boundary conditions which, themselves of Watson and Crick that this redun- duces the improbability of occurrence being independent of the physical dancy does not prevent DNA from of any particular sequence and thereby chemical forces in which they are eSectively functioning as a code. I enables it to have a meaning-a mean- rooted, control the mechanism of life accordingly disregard, for the sake of ing that has a mathematically deter- in the developed organism. brevity, the redundancy in the DNA minate information content equal to To elucidate this transmission is a code and talk of it as if it were func- the numerical improbability of the major task of biologists today, to which tioning optimally, with all o£ zfs alterna- arrangement. I shall return.

21 JUNE 1968 1309

This content downloaded from 128.103.149.52 on Wed, 15 Jul 2015 16:00:49 UTC All use subject to JSTOR Terms and Conditions Some Accessory Problems Arise Here of a higher principle over a system motion of a heavy body is controlledby under dual control can have any value the gradient of potential energy. We have seen boundary conditions down to zero may allow us also to Rememberhow Driesch and his sup- introducing principles not capable of conceive of the continuous emergence porters fought for recognition that life formulation in terms of physics or of irreducible principles within the transcends physics and chemistry, by

* . P . , chemistry into inanimate artifacts and orlgln ot lte. arguing that the powers of regeneration living things; we have seen them as in the sea urchin embryo were not exS necessary to an information content in plicable by a machinelike structure, a printed page or in DNA, and as in- We Can Now Recognize and how the controversyhas continued, troducing mechanical principles into Additional Irreducible Principles along similar lines, between those who machines as well as into the mechanisms insisted that regulative ("equipotential" of life. The irreducibility of machines and or "organismic")integration was irreZ Let me add now that boundary con- printed communications teaches us, al- ducible to any machinelike mechanism ditions of inanimate systems established so, that the control of a system by irre- and was therefore irreducible also to by the history of the universe are found ducible boundary conditions does not the laws of inanimatenature. Now if, as ln the domains of geology, geography, interfere with the laws of physics and I claim, machines and mechanical proc- and astronomy, but that these do not chemistry. A system under dual control esses in living beings are themselves form systems of dual control. They relies, in fact, for the operations of its irreducibleto physics and chemistry,the resemble in this respect the test-tube higher principle, on the working of situation is changed. If mechanistic and type of boundaries of which I spoke principles of a lower level, such as the organismicexplanations are both equally above. Hence the existence of dual con- laws of physics and chemistry. Irre- irreducible to physics and chemistryS trol in machines and living mechanisms ducible higher principles are sldditionszI the recognition of organismic processes represents a discontinuity between ma- to the laws of physics and chemistry. no longer bears the burden of standing chines and living things on the one The principles of mechanical engineer alone as evidence for the irreducibility hand and inanimate nature on the other ing and of communication of informa° of living things. Once the "field"-like hand, so that both machines and living tion, and the equivalent biological prin powers guiding regeneration and mor- mechanisms are irreducibleto the laws ciples, are all additional to the laws phogenesis can be recognized without of physics and chemistry. of physics and chemistry. involving this major issue, I think the Irreducibility must not be identified But to assign the rise of such addiQ evidence for them will be found to be

. * . with the mere fact that the joining of tional controlling principles to a selec convlnclng. parts may produce features which are tive process of evolution leaves serious There is evidence of irreducibleprinZ not observed in the separate parts. The difficulties.The production of boundary ciples, additional to those of morpho- sun is a sphere, and its parts are not conditions in the growing fetus by trans- logical mechanisms,in the sentience that spheres, nor does the law of gravitation mitting to it the information eon- we ourselves experience and that we ob- speak of spheres; but mutual gravita- tained in DNA presents a problem. serve indirectly in higher animals. Most tional interaction causes the parts of Growth of a blueprint into the cotnples biologists set aside these matters as un- the sun to form a sphere. Such cases tnachinery that it describes seems to profitable considerations. But again, of holism are common in physics and require a system of causes not specifi- once it is recognized, on other grounds, chemistry.They are often said to repreS able in terms of physics and chemistrys that life transcends physics and chem- sent a transition to living things, but such causes being additionalboth to the istry, there is no reason for suspending this is not the case, for they are reg boundary conditions of I)NA and to recognition of the obvious fact that ducible to the laws of inanimatematter, the morphological structure brouglht consciousness is a principle that funda while living things are not. about by DNA. tnentally transcends not only physics But there does exist a rather different This missing principle which builds and chemistry but also the mechanistic continuity between life and Inanimate a bodily structure on the lines eiT arL principlesof living beings. nature. For the beginnings of life do instruction given by DNA may be exS rlot sharply differ from their purely emplified by the far-reaching regenera- phys;cal-chemicalantecedents. One can tive powers of the embryonicsea urchin, Biological Hierarchies C:onsistof reconcile this continuity with the ird discovered by Drieschg and by Paul a Series of BouxldaryConditions reducibilityof living things by recalling Weiss's discovery that completely slis the analogous case oiEinanimate arti- persed embryonic cells will grow, when The theory of boundary conditions iSacts. Take the irreducibility of maZ lumped togetherg into a fragment o£ recognizes the higher levels of life as chines; rlo animal can produce a ma- the orgalnLfrom which they were iso fortninga hierarchy,each level of which chine, but some animals can nzake lated (3)0 We see an integrativepower relies for its workings on the principles primitive tools, and their use of these at work here, characterizedby Spemana of the levels below it, even while it tools nzay be hardly distinguishable and by Paul Weiss as a "field9' (4)9 tself is irreducibleto these lower prin from the mere use of the animal'slimbse which guides the growth of tEbryONiG ciples. I shall illustrate the structure of Or take a set of sounds conveying inffl fragments to form the rnorphological such a hierarchy by showing the way fortnation; the set of sounds can be so features to which they embryologically five levels make up a spoken literary obscured by Iloise that its presence is belong. These guides of morphogexlesis composition. x10 longer clearly identifiable. We can are given a fortnal expression in WadF Ishe lowest level is the production of sayS then, that the control exercised dington's "epigenetic landscapes" (5)e a voice; the second, the utterance of by the lbolmdaryconditions of a sys- They say graphically that the growth words; the third, the joining of words tem can be reduced gradually to a of the embryo is controlled by the gra t69nnake sentences; the fourth, the work valaishingpoint. The fact that the effect dient c)f potential shapes, much as the ing of sentences intcs a style; the fifth, 1310 SCIENCE, VOL. 160

This content downloaded from 128.103.149.52 on Wed, 15 Jul 2015 16:00:49 UTC All use subject to JSTOR Terms and Conditions and highest, the composition of the text. harnesses it to the service of the next- anism is not revealed by its physical- The principles of each level operate higher level, and this control is trans- chetnical topography. We can say the under the control of the next-higher mitted stage by stage, down to the basic same thing of all higher levels: their level. The voice you produce is shaped inanimate level. description in terms of any lower level into words by a vocabulary; a given The principles additional to the do- does not tell us of their presence. We vocabulary is shaped into sentences in main of inanimate nature are the prod- can generally descend to the compo- accordance with a grammar; and the uct of an evolution the most primitive nents of a lower level by analyzing sentences are fitted into a style, which stages of which show only vegetative a higher level, but the opposite proc- in turn is made to convey the ideas of functions. This evolutionaryprogression ess involves an integration of the the composition. Thus each level is is usually described as an increasing principles of the lower level, and this subject to dual control: (i) control in complexity and increasing capacity integration may be beyond our pow- accordance with the laws that apply for keeping the state of the body in- ers. to its elements in themselves, and (ii) dependent of its surroundings. But if In practice this difficulty may be control in accordance with the laws we accept, as I do, the view that tiving avoided. To take a common example, of the powers that control the com- beings form a hierarchy in which each suppose that we have repeated a particu- prehensive entity formed by these ele- higher level representsa distinctiveprin- lar word, closely attending to the sound ments. ciple that harnesses the level below- it we are making, until these sounds have Such multiple control is made pos- (while being itself irreducibleto its lower lost their meaning for us; we can re- sible by the fact that the principles principles), then the evolutionary se- cover this meaning promptly by evok- governing the isolated particulars of a quence gains a new and deeper signifi- ing the context in which the word is lower level leave indeterminate condi- cance. we can recognlze. then a strictly commonly used. Consecutive acts of tions to be controlled by a higher princi- defined progression, rising from the in- analyzing and integrating are in Ieact ple. Voice productionleaves largelyopen animate level to ever higher additional generally used for deepening our un- the combination of sounds into words, principles of life. derstanding of complex entities com- which is controlled by a vocabulary. This is not to say that the higher prising two or more levels. Next, a vocabulary leaves largely open levels of life are altogether absent in Yet the strictly logical diSerence be- the combination of words to form sen- earlier stages of evolution. They may tween two consecutive levels remains. tences, which is controlled by grammar!l be present in traces long before they You can look at a text in a language and so on. Consequently,the operations become prominent. Evolution may be you do not understand and see the let- of a higher level cannot be accounted seen, then, as a progressive intensifica- ters that form it without being aware for by the laws governing its particulars tion of the higher principles of life. of their meaning, but you cannot read on the next-lower level. You cannot de- This is what we witness in the develop- a text without seeing the letters that rive a vocabulary from phonetics; you ment of the embryo and of the growing convey its meaning. This shows us two cannot derive grammar from a vocabu- child - processes akin to evolution. diSerent and mutually exclusive ways lary; a correct use of grammardoes not But this hierarchy of principles raises of being aware of the text. When we account for good style; and a good style once more a serious difficulty. It seems look at words without understanding does not supply the content of a piece impossible to imagine that the sequence them we are focusing our attention on of prose. of higher principles, transcending fur- them, whereas, when we read the wordss Living beings comprise a whole se- ther at each stage the laws of inanimate our attention is directed to their mean- quence of levels forming such a hier- nature, is incipiently present in DNA mg as part ot a language. We are aware archy. Processes at the lowest level are and ready to be transmitted by it to then of the words only subsidiarily, as caused by the forces of inanimate na- the offspring. The conception of a blue- we attend to their meaning. So m the ture, and the higher levels control, print fails to account for the kansmis- first case we are looking at the words, throughout, the boundary conditions sion of faculties, like consciousness, while in the second we are looking from left open by the laws of inanimate na- which no mechanical device can possess. them st their meaning:the reader of ture. The lowest functions of life are It is as if the faculty of vision were to a text has a from-atknowledge of the those called vegetative. These vegetative be made intelligible to a person born words' meanings while he has only a functions, sustaining life at its lowest blind by a chapter of sense physiology. from awarenessof the words he is read- level, leave open-both in plants and in It appears, then, that DNA evokes the ing. Should he be able to shift his at- animals-the higher functions of growth ontogenesis of higher levels, rather than tention fully toward the words, these and in animals also leave open the determining these levels. And it would would lose their linguistic meaning Ieor operations of muscular actions. Next, follow that the emergence of the kind him. in turn, the principles governing mus- of hierarchy T have defined here can Thus a boundary condition which cular actions in animals leave open the be only evoked, and not determined,by harnesses the principles of a lower level integration of such actions to innate atomic or molecular accidents. How- in the service of a new, higher level patterns of behavior; and, again, such ever, this question cannot be argued establishes a semantic relation between patterns are open in their turn to be here. the two levels. The higher comprehends shaped by intelligence, while intelli- the workings of the lower and thus gence itself can be made to serve in man forms the meaning of the lower. And as the still higher principles of a respon- Understanding a Hierarchy we ascend a hierarchyof boundaries, sible choice. Needs "fromat" Conceptions we reachto ever higherlevels of mean Each level relies for its operations ing. Our understandingof the whole on all the levels below it. Each reduces I said above that the transcendenceof hierarchicedifice keeps deepeningas the scope of the.one immediatelybelow atomism by mechanism is reflected in we move upward from stage to it by imposing on it a boundary that the fact that the presence of a mech- stage. 21 JUN:X3l968 131t

This content downloaded from 128.103.149.52 on Wed, 15 Jul 2015 16:00:49 UTC All use subject to JSTOR Terms and Conditions The SequexIceof Boundaries integrating admittedly leaves open our common sense knows it to be free. The mind itself includes an ascending lBears on Our SciexItificOutlook tnany dangers. Detailing tnay lead to pedantic excesses, while too-broad inZ sequence of princlplesv Tts appetitive The recognition of a whole sequence tegrationsmay present us with a mean and lntellectual workings are tran- of irreducibleprinciE)les transforms the dering impressionisin.But the prinLciple scended by principles of responsibility logical steps for understandingthe uni- of stratified relations does oSer at Thus the growth of man to his highest verse of living bemgs-The idea, which least a rational framemtorkfor an in levels is seen to take place along a se- comes to us iEromGalileo and Gassendi, quiry into living things and the prod quence of rislng principles.And we see that all manner of things tnust ulti- ucts of human thought. this evolutionary hierarchy built as a xnately be understood in terms of-mat- I have said that the analytic descent sequence of boundaries, each opening ter in motion is refutedvThe spectacle from higher levels to their subsidiariesi5 the way to higher achievementsby har- 6zf physical tnatter forming the basic usually feasible to some degree, while nessing the strata below them, to which tangible ground of the universe is found the integrationof items of a lower level they themselves are not reducible.These to be almost empty of meaning. The so as to predict their possible meaning boundaries control a rising series o£ universal topographyof atomic particles in a higher context may be beyorld the relations which we can understandonly (witlhtheir velocities and forces) which, range of our integrative powerse I may lry being aware of their eonstituentparts accordirlg to Laplace, oSers us a un;- add now that the same things may be subsidiarilySas bearing on the upper versal knowledge of all things is seen seen to have a joint meaning when [evel which they serve. l:o contain hardly any knowledge that viewed from one point, but to lack The recognition of certain basic im is of mterest. The claims made, follow- this counection when seen iErotnanother possibilitieshas laid the foundations of ing the discovery of DNA, to the effect point. Frotn an airplane we can see the some major principles of physics and that a11study of life could be reduced traces of prehistoric sites whichs °ver chemistry, siinilarly, recognition of the tventually to molecular biology, have the centuries, have been unnoticed bt inpossibility of understanding living shown once more that the Laplacean people walking over them; indeed, ollce things in terms of physics and chemistry, idea of universal knowledge is still the he has landed, the pilot himself xnay no far from setting limits to our under- theoreticaJLideal of the natural sciences; longer see these traces. standingof life, will guide it in the right current opposition to these declarations The relation of mind to body has a direction. And even if the demonstraS has often seemed to confirm this ideal, similar structure. The mind-body prob tion of this impossibility should prove Ebydefending the study of the whole lem arises from the disparity between of no great advantage in the pursuit organism as being only a temporary the experience of a person observing an 6>f discovery, such a demonstration approach. But now the analysis of the external object-for example,, a cat would help to draw a truer image of hierarchy of living things shows that and a neurophysiologist observing tlhe life and man than that g;ven us by the to reduce this hierarchy to ultimate par bodily mechanism by means of wlhich present basic concepts of biology. ticulars is to wipe out our very sight the person sees the cat. The diSerence of it. Such analysis proves this ideal arises from the fact that the person to be both false and destructive. observingthe cat has a from-knowledge Summary Each separate level of existence is of of the bodily responses evoked by the course interesting in itself and can be light in his sensory organs and this Mechanisms, whether man-made or studied in itself. Phenomenology has from-knowledge integrates the joint morphological,are boundary conditions taught this, by showing how to save meaning of Rtheseresponses t } form the harnessingthe laws of inanimatenatureS higher, less tangible levels of experience sight of the cat, whercas the neurophys- being themselves irreducible to those by not trying to interpretthem in terms iologist, looking at these responsesfrom lawsOThe pattern of organic bases in of the more tangible things in which outside, has only an at-knowledge o£ DNA whiclhfunctions as a genetic code their existence is rooted. This method them, which, as such, is not integrated is a boundary condition irreducible to was intended to prevent the reduction to form the sight of the cat This ig physics and chemistry. Further control- of man's mental existence to mechanical the same duality that exists between the ling principlesof life may be represented structures. The results of the method airman and the pedestrian in interprct as a hierarchy of boundary conditions were abundantand are still Rowing,but ing the same traces, and the same that extending, in the case of man, to con- phenomenology left the ideal of exact exists between a person who, when sciousness and responsibility. a sees its science untouched and thus failed to reading written sentence, References and Notes secure the exclusion of its claims. tneaning and another person who, being 1. More precisely, each item consists of one Thus, phenomenological studies re- ignorant of the language, sees only the out of four alternatives consisting in two positions of two different compound organic mained suspended over an abyss of writing. bases. reductionism. Moreover, the relation of Awareness of mind and body con- 20 The blueprint carried by the DNA molecule of a particular zygote also prescribesindividq the higher principles to the workings of front us, therefore with two diSerent ual features of this organism,which contribute things. The mind harnesses neurophys- to the sources of selective evolution, but I the lowest levels in which they are shall set these features aside here. rooted was lost from sight altogether. iological mechanisms and Is 1lot de 3. See P. Weiss, Proc. Nat. Acad. Sci. U.S. 42, 819 (1956). I have mentioned how a hierarchy termined by them. Owing to the exist 4. The "field" concept was first used by Spemann controlled by a series of boundary prin- ence of two kinds of awareness-the (1921) in describingthe organizer;Paul Weiss (1923) introduced it for the study of regener- ciples should be studied. When examin- focal and the subsidiarwe can now ation and extended it (1926) to include ing any higher level, we must remain distingulsh sharply between the mind ontogeny. See P. Weiss, Princaples of Developw ment (Holt, New York, 1939 ), p. 290. subsidiarily aware of its grounds in as a 4'from-at"experience and the sub 5> See, for example, C. H. Waddington? The seen focally Strstegy of the Genes (Allen & Unwine London, lower levels and, turning our attention sidiaries of this experience, 1957), particularly the graphic explanation of 1Lothe latter, we must continue to see as a bodily mechanism.We can see then "genetic assimilation" on page 167. 6. See, for example, M. Polanyi, Amer. PsycholZ em as bearing on the levels above that, though rooted in the bodyg the ogist 23 (Jan. 1968 ) or , The Tacit themv Suob alternationof detailing and mind is free in its actions-exactly as Dimensiozz (Doubleday, Nevr York, 1967). SCIENCE} VOL. 160

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